Simulation Cover Grate

Hi Guys, i was wonering if any of you can please help me on a quick simulation. i have a cover grate modelled up which consits of a 40 x 40 box section frame with 6mm steel welded on top with 40 x 10 bracing every 300mm underneath. the clear opening of the hole is 1200 x 240 which allows the box section frame to rest on. i tried simulation a point load force on this in the centre and it was showing way crazy results like showing the plate on top spewing through.

I basically want to test it to see what the maximul load it can take but for some reason it is not going too well. can someone please simulate thsi as i am unsure on the fixing as it is not blted down and it just rest on top of a fixed hole.

I have attached my models and pictures and will greatly appreciate it if someone can help me with this

Thanks for your interesting article. I am due to start a simulation 3 day course in 2 weeks which should hopefullycover all this . If possible can you please run my simulation and check it is correctly setup as I need to know what the maximum force the cover grate can check

see previous response "otherwise the setup looks fine. but remember you want at least 2 elements across a thickness. which is why beams would be a better fit for this."

"setup correctly" is a relative phrase. the problem is setup the way you describe and should show the basics of the behavior you're expecting. but i'd still go through a mesh convergence test and look at beams. and also vary the loads a little bit to see if it trends the way you expect. it is unlikely that the 3day training will cover this to the leve you're expecting. we offer a service called mentoring where we go through the assumptions your analysis makes..etc and work with you one on one to setup your analysis and understand the results it gives.